Question of the Week

Can you get sick from your own intestinal bacteria?

Sat, 14th Jul 2012

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Claes Gauffin asked:

Much food related illnesses come from contamination by intestinal bacteria due to poor hygien in meal preparation. The question is: Will the culprit self, i.e the person whose bacteria got into the food, be sick as well? In other words, can you get sick from your own intestinal bacteria?






Hannah -   So, can your own bowel bugs make you sick or can only make other people sick?

According to Professor Liz Sockett at Nottingham University, the mucosal lining of your gut contains immune cells which make antibodies which will attack and neutralise specific bacteria.  The immune system will remember seeing the specific bacterium if it re-infects.  So for the second exposure, the immune system will probably neutralise and kill the bacterium before it can multiply sufficiently to cause disease.  But some food poisoning isnít caused by the bacteria growing in the individual, but by the toxins produced by bacteria in food that has been poorly stored. 

E. coli bacteriaThe toxin damages your intestinal wall lining so quickly that you havenít got the time to mount an immune response to protect yourself.  So, immunity cannot protect you and you could show symptoms on repeat exposure to the toxin.

Staphylococcus Aureus for example which can be found on the skin where it causes boils and spots, if that gets into poorly stored food, produces toxins which are heat and acid stable.  So, the bug may not survive in the cooking process and the acid environment in your stomach, but the toxin does, and it can poison your intestine, causing diarrhoea and vomiting.

Harry Flint, Professor of Rowett Institute of Food and Health at Aberdeen University explainsÖ

Harry -   Intestinal damage and diarrhoea caused by the huge quantities of toxin present in the food, and produced by the bacteria multiplying in the food, can affect you even if you have acquired immunity to the bacteria.


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You betcha! Geezer, Mon, 9th Jul 2012

It is my belief that you can not in fact self-infect with a disease.

However, there are many caveats to this.

Staph Aureus, for example, colonizes a few individuals.  It also produces a toxin, so if allowed to overgrow in food, it will cause short-term diarrhea, likely irrespective to whether a person is colonized with the bacteria. 

Sometimes antibiotics, or anti-fungals will cause an imbalance of flora, and cause GI problems with overgrowth of certain types of flora.

It is a major problem to get bacteria where it is not supposed to be.  So, for example a GI gunshot can rapidly cause sepsis if bacteria is allowed to escape into the abdominal cavity.

Not bacteria per-se, but many macro-organisms such as Lice or worms aren't effectively killed by the immune system, and one can be re-infected if they are eliminated. 

Chicken pox is one disease that children often get.  However, the virus can lay dormant in the body for decades, only to return as shingles (and also be infective to others).

CliffordK, Mon, 9th Jul 2012

On the question "Will ... the person whose bacteria got into the food, be sick as well?", the answer is: Not always.

In most cases, a person will develop an immunity to a disease, and clear the pathogen from their system (or they develop a chronic infection, and perhaps die).
However, some people are not badly affected by the pathogen, do not develop an immunity and do not clear the microorganism from their system; these "carriers" can continue to shed the pathogen for their whole life.
One of the most infamous cases was "Typhoid Mary", who had no symptoms of Typhoid fever, but managed to infect many people in her occupation as a cook, and some died. See

The same can happen for many microorganisms; gut bacteria in particular are somewhat protected from the immune system. Helicobacter Pylori causes stomach ulcers in some people, but most infected people are symptom-free. evan_au, Mon, 9th Jul 2012

Actually, the vast majority of bacterial infections are self infections. Its a matter of bacteria that normally live harmlessly or even helpfully in one part of the body finding their way into another part of the body where they are not supposed to be. For example, most urinary tract infections are caused by your own intestinal bacteria invading the urethra and making their way into the bladder. Another example would be your own bacteria on the surface of the skin getting into deeper tissues either through a wound or a surgical incision. Or intestinal or throat bacteria making their way deep into the lungs and causing pneumonia. There are relatively few out right pathogens that you "catch" from someone else like Group A strep that causes strep throat, or salmonella from food, and even fewer now because we can vaccinate for many of them. cheryl j, Wed, 11th Jul 2012

Yes, I mentioned that there were issues with getting bacteria where they're not supposed to be.  Some of the most damaging bacteria infections occur when normal skin bacteria colonize surgical implants such as artificial joints.

Most of the current vaccines are for viruses, and not for bacteria, with the two big bacterial vaccinations being pneumococcus, and meningicoccus. CliffordK, Wed, 11th Jul 2012

A few other bacterial vaccines -Haemophilus influenza, pertussis, diptheria, tetanus. Some less common vaccines -  TB and plague, cholera, and the salmonella species that causes typhoid. i read they have a vaccine for E coli 0157 now to start using in cattle. cheryl j, Sun, 12th Aug 2012

"eat shit & die"= maybe esophagus cant acidize like stomach? CZARCAR, Sun, 12th Aug 2012

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